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Old January 18th, 2005, 01:45 PM   #1
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"diagonal erect image"

has anyone googled "diagonal erect image"?

There are enclosed prisms for astronomy.. stuff.
There are 45 degrees ones (the camcorder would sit at a 45 degree anlge, like the MovieTube adapter) and (less available) inline ones.

You find them from 40USD to 200 or more.

But most of them are 1-1/2'' in diameter. The few available 2'' (for larger lenses, like the GL2/XM2) are 90degrees...

Oh, just search it and see what I mean! :)
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Old January 18th, 2005, 02:09 PM   #2
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The diameter is too small for the image (45 degree version).
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Old January 18th, 2005, 02:22 PM   #3
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Edmund Optics sells several prisms that could be used to construct an erecting mini35 type system. I'm glancing at the the catalogue and they have:

Amici Roof Prisms
Penta Prisms
Schmidt Prisms (45 deg)

Unfortunately the largest amici and schmidt prisms are 25mm wide. We need something around 50mm. The penta prisms on the other hand come in 50mm sizes but do not affect the images left/right and up/down orientation unfortunately.

What do the mini35 and Movietube use?
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Old January 18th, 2005, 02:25 PM   #4
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Mini35 -> one mirror and two 90s.

Movietube -> Custom Schmidt
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Old January 18th, 2005, 07:37 PM   #5
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Isn't this exactly what I'm looking for in my thread? (35mm double cameras)
Is it really a prism to look in 45° or 90°. If it is, does it loose much light and isn’t it possible to make it with glass planes cemented together and than filled with a transparent fluid?

Just a tought.
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Old January 19th, 2005, 04:58 AM   #6
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I've googled "telescope diagonals".

So, more info on diagonals (they do use Amici prism - some of them):

http://www.sctscopes.net/SCT_Tips/Eyepieces/Diagonals/diagonals.html

Down the page you'll find this particular product:
http://www.buytelescopes.com/product.asp?t=54&pid=4331&m=49

(200$ and 10% light loss..)

Some more 2'' diagonals (they say "visual light efficiency of over 98%. "; unfortunately, at 90degrees):
http://www.meridiantelescopes.com/diagonals.htm

More on digonals:
http://www.mailbag.com/users/ragreiner/arpert.html#Diagonals

aaaaand more:
http://www.cloudynights.com/articles/diagonals.htm

I guess the diameter of the "diagonal" should match the 35mm frame size.. (24/36mm - about 43mm on digonal), or maybe a bit smaller, if you're ok with that.
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Old January 19th, 2005, 11:03 AM   #7
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On one of these sites, you can see the prism is just a triangle. Do you think it's more than that? Maybe there is a mirrored face inside.
Anyway, does anyone know how much light these things absorb?
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Old January 19th, 2005, 12:54 PM   #8
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somewhere between 1% to 10% (as I understand in the first link).

And they are "diagonals" with just a mirror (non erecting) and erecting digonals, with Amici prisms and such...
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Old January 20th, 2005, 11:08 AM   #9
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Let me correct my previous post. I just realized that Edmund does sell a Schmidt prism that is large enough for erecting a 35mm frame! If only one could figure out a way to deal with the darn 45 degree angle (I suppose we could try to build a "DIY movietube"...).
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Old January 20th, 2005, 11:11 AM   #10
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I happen to like the 45degrees angle! :) So, that is not a problem for me.
Do you have a link, Aaron?
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Old January 20th, 2005, 11:17 AM   #11
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The 45 degree angle is certainly cool looking, don't get me wrong! It would just require more money to be spent and the necessity for a rail system.

Here is the link:

http://www.edmundoptics.com/onlinecatalog/displayproduct.cfm?productID=2430&search=1

Second listed item. It occured to me that the faces which matter for us are faces C and E both of which are over 40mm! Should be perfect for out application!

The only dowside is, of course, the cost.
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Old January 20th, 2005, 11:31 AM   #12
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argh! Expensive! (for me)

But thanks for the link.
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Old January 20th, 2005, 06:16 PM   #13
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James you mention 2? 90s and a mirror? Why two right angle prisms? I would think one would do just fine.
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Old January 20th, 2005, 10:14 PM   #14
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Just a link to refference prism designs:
http://www.tecplusplus.de/ManualLu/prisms.htm
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Old January 20th, 2005, 10:18 PM   #15
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Yeah I've been looking for a pechan prism (as they list there) for a while now. No luck. I've considered buying a pair of large diameter binoculars and hacking them apart in hopes of finding a large enough erecting prism.....
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